Why Are Spaces and Unicode Characters Often Restricted in Passwords?

It's interesting to think about how older computers handled passwords. For example, back in the day, you could type special CTRL characters as part of your password on some systems! But now, most sites should allow a wider range of characters. Password management tools and processes have evolved, so there’s generally no harm in letting users pick complex passwords.

I think the issue might be that users inadvertently copy-paste passwords with extra spaces, making them fail during validation. Trimming leading and trailing spaces could help here. But there's really no technical reason to restrict spaces, other than legacy practices.

This might stem from historical practices where systems had trouble handling spaces and special characters properly. Especially in command-line environments, where space could confuse the system. Nowadays, many platforms accept spaces and non-ASCII characters, and OWASP even suggests allowing Unicode for stronger passwords.

I believe it’s mostly about keeping things user-friendly. If users can't easily type a password or if they write it down incorrectly, it leads to more support issues. Some services keep it simple and stick to basic ASCII just to avoid potential headaches.

Actually, not all systems restrict spaces or Unicode characters in passwords. Some have outdated software, which might explain their limits. For example, Reddit even allows emoji in passwords! So it really depends on the service you're using.